Water kefir grains need minerals to survive and thrive and benefit from water sources with higher mineral content. With that said, if the mineral content is too high, the grains can begin to disintegrate.
Some water sources such as well water or spring water are naturally high in mineral content, are ideal for making kefir and can be used straight out of the tap. Sometimes well water is too high in minerals though and can cause your grains to disintegrate. Use your discretion. Avoid distilled water, reverse osmosis water, and water which has been filtered through an activated carbon filter such as a Britta or Pur. They strip the water and often have extremely low or non-existent mineral levels.
The Sentiva or Berkey water filters are a great choice because the minerals are added back into the water. If you prefer to purchase water, then natural spring water is the best choice.
Structured, alkalized, or pH-adjusted water is not appropriate for culturing water kefir.
Still have questions about your specific water filter? Google your brand name and see if it contains minerals once it is filtered.
Tap Water is the best!
When using tap water, I recommend boiling the water for 10 minutes to help remove chlorine. You can also let your tap water stand for 24 hours instead of boiling it to help the chlorine evaporate.